You may add a new credit card via the Account Settings page, only after your current subscription expires. To do this:
-- Log in to your Piktochart account and cancel future billing for your current payment source. Find your User ID in the upper righ and look for Account Settings>Plans & Billings. There you'll find the option to cancel recurring billing. Your current subscription will continue through its purchased term.
-- When your current subscription expires, you'll find the LEVEL UP option reappears upon log-in. That indicates you can then re-subscribe and provide your new payment source at check-out. Your Saved Visuals will always remain safely stored on the account even during this brief transition.